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Thanks to a persistent stream of injuries and Ryan Braun’s suspension, the 2013 Milwaukee Brewers provided plenty of opportunities for young position players. Some of those players delivered impressive performances, albeit for only a few months of the 2013 season. What do those part-time performances tell us about their actual ability?

The all-too-common answer is nothing at all. This is not correct. Certainly, you can’t drive the true measure of a player solely from only a few months of play, much of which could have been driven by luck. But while luck plays a strong role in the ebb and flow of baseball performance, luck is still bounded by the principle of regression to the mean. As many readers know, players in baseball and other sports tend to regress statistically toward the major league average for similar players: above-average performances tend to decline, and below-average performances tend to improve. So, the truth is that you can use partial-season performances to derive a player’s true ability, but only if you properly combine the player’s on-field performance with the likelihood that his performance will move back toward the league average.

Fortunately, this adjustment can be made using a weighted average. This means assigning a certain percentage weight to the performance the player actually displayed, and the remainder to the major league average for that statistic. When you add the two figures back together, you end up with the “regressed” version of the player’s ability: a better prediction of what that player actually is, and probably will be going forward. This analysis needs to be run separately for each baseball statistic that interests you. Each statistic has its own stabilization factor, the point at which the player has enough plate appearances to make his performance worth considering. The stabilization factor dictates how you combine the player’s actual performance with the major league average for that statistic to project the player’s true ability.

Unfortunately, a few months in the big leagues does not provide enough plate appearances to assess your favorite measures of hitter productivity—on-base percentage (OBP), on-base-plus-slugging (OPS), or weighted on-base average (wOBA). However, three peripheral statistics can be evaluated: (1) Walk Percentage (BB%), (2) Strikeout Percentage (K%), and (3) Home Run Percentage (HR%). These statistics are not as all-encompassing as the others, but they do measure the player’s performance in three core areas. For ease of discussion, I also extrapolated home run percentages to roughly an entire season (500 adjusted plate appearances), to provide a sense of each player’s full-season home run ability. Everybody loves home runs.

I’m happy to answer questions on the math for those actually interested, but for now, let’s proceed to the results. For this first article, we’ll look at the two players whose 2013 batting numbers surprised people the most: Khris Davis and Scooter Gennett.

Khris Davis

In part-time duty, Khris Davis had a monster campaign, serving as Ryan Braun’s primary replacement in left field after Braun was suspended. As I’ve previously noted on Twitter, Davis replaced Braun in more ways than one: Davis was equally effective at producing runs in 2013 as Braun was in his terrific 2012 season. (2013 Davis: 160 wRC+, .949 OPS; 2012 Braun: 161 wRC+, .987 OPS). That’s saying something.

But, we need to regress Davis’s numbers to fairly predict his true ability. The following table provides Davis’s actual statistics from 2013, along with his regressed (“Reg.”) numbers:

PA

HR

K Rate

Reg. K

BB Rate

Reg. BB

HR Rate

Reg. HR

’13 Actual HR Pace

’13 Regressed HR Pace

153

11

22%

21%

7%

8%

11%

7%

46

28

These numbers are encouraging. Essentially, Davis projects the ability to walk about 8% of the time (league average) and strike out about 21% of the time (also, basically league average), despite hitting for tremendous power.

On the subject of power, Davis’s home run rate is astonishing. Had he maintained the same pace over the entire 2013 season, Davis would have hit at least 46 home runs: more than Miguel Cabrera and second only to the ironically-named Chris Davis of the Orioles.

Even assuming full regression to the mean, Davis still projects to hit at least 28 home runs in a full starting role. Although 28 home runs is certainly less than 46, only 18 players in baseball — out of 955 who grabbed a bat this year — hit at least 28 home runs. Those players averaged a wRC+ of 132 and an OPS of .858.

These numbers explain why the Brewers are rumored to be asking Ryan Braun to move to right field (the Brewers will never have better leverage) in order to get Davis into the lineup in left field. Although Davis is considered below-average defensively, an outfielder with top-20 home run ability belongs in the starting lineup, particularly at Miller Park. Although his regressed statistics bring Davis slightly down to earth, they far exceed the recent offensive production provided by Norichika Aoki.

Scooter Gennett

Before his call-up, many scouts derided Gennett as a one-trick pony: a groundball hitter who couldn’t draw walks, had minimal power, was a poor defender, and would never be a complete player. Gennett was called up anyway, first to platoon with a floundering Rickie Weeks, and then to replace him when Weeks finished the season on the disabled list.

Gennett turned out to be a satisfactory defender at second base, as well as a decent base runner. He doesn’t draw anywhere near enough walks (4% of PA in 2013), but the regression suggests his ability is better than that (6%), if still below-average. A below-average walk percentage is tolerable if you consistently put the ball in play, which is one thing Gennett has always done: his .324 batting average in 2013 is not out of line with his career numbers in the minors. And if I could hit .324, I probably wouldn’t be that patient at the plate either.

The most surprising thing about Gennett, though, was his power. His 2013 slugging percentage was an excellent .479, and he hit home runs at a rate that would have culminated in a 15 home run season. Given Gennett’s paltry home run rate in the minors, this number was suspicious. But, even when regressed, his home run ability appears to be … 15 home runs a season. The Brewers would be delighted with 15 home runs from Gennett, particularly combined with anything resembling the hitting he provided in 2013: a 131 wRC+ (.834 OPS). He has shown problems hitting other lefties, but he has earned the right to demonstrate improvement, and his platoon split is already baked into his otherwise-solid offensive numbers.

To give credit where it is due, the scouts of Baseball Prospectus, in their 2013 Futures Guide published back in May, were more bullish on Gennett than the consensus I cited above. They projected Gennett to be an average defender, a solid baserunner, and a “tough out” who had some ability to hit for power and the potential to be an average major leaguer.

Even after regression, Scooter Gennett projects to be a significant overall upgrade from Rickie Weeks. Gennett was also only 23 years old this year, and has several years to reach his prime. His regressed statistics do not raise any red flags. On balance, Gennett looks to be at least an average starter next season at second base, which would be a significant upgrade from what the Brewers have endured as of late.

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Comments

Tell us what do you think.

Luke says:October 23, 2013

Great post, been wondering about this very subject since season’s end. Does this mean the Brewers are in a position to unload some veteran “talent” and replenish their depleted farm system, or do these young guys still need a safety net for next year?

If there is a particular equation that interests you, let me know and I’ll post it. But, the method I’m following isn’t something I made up; you can find it in Derek Carty’s original article. http://www.baseballprospectus.com/a/14215

1. Is it best to weigh Scooter and Davis against league average? Scooter’s minor league numbers suggest he’ll never have average HR power in the majors (not sure on Davis, but I’m skeptical), wouldn’t you need to weigh his August/September production against his MLB projections (like Zips or whatever you want to use) instead of what the average major league player does?

Starting with average MLB player as a baseline might inflate their projections.

2. In special regard to Scooter, he was primarily a platoon player last year, did you make adjustments for that? If he has 230 PAs last year in primarily a platoon role, a season in the platoon role might only be 450-500 PAs, not the normal 650 or whatever, that would impact a raw stat like HRs

Andy’s first question is great, and something I was going to address in the follow-up article. How reasonable is the assumption to apply league average? I think it happens to be particularly reasonable when I’m looking at players who outperformed major league peripherals in at least one category in a limited stint. And using something other than league averages is problematic; the returns on getting more specific start to diminish fast, and if you can truly peg a player well enough to find the perfect comp for him (which is impossible), then you would have nothing left to project. Tom Tango generally agrees with this, so again, it’s not just me.

I did not take into account a platoon projection; I assumed being a full-season starter. Fewer PAs equals fewer opportunities, certainly. I think the platoon issue for Gennett is overblown and he’s entitled to a few months of being a full-time starter to see if he can sort it out.

The numbers might suggest that Davis is capable of a 28 HR type of season, but it doesnt really reflect the fact that he spent a lot of time facing pitchers who had never seen him before, and who didnt have a good scouting report. Davis has one of the most horrible swings I have ever seen in the game, and his late season fade is a big cause for concern. He probably could be a 20 HR type of guy, but he also, scouting wise, project to be a 150 K guy who can only hit about .250 and play horrible defense. That is not a good player by any means really. The fact that the Brewers are even considering moving Braun becuase of this guy just proves how little they know about what they are doiing.

Gennett should be a league average player, and no reason at all to suspect that he wont get the starting job at 2B after Weeks is gone.

Davis does dramatically fly open when he swings, but somehow he drives the ball with power to the opposite field.

I don’t think the Brewers should be chastised for asking Braun to move to RF. The move makes sense if Davis is more valuable than Aoki. Why would you not play your best offensive players? A .260/.360/.460 line from Davis is more valuable than the .290/.360/.400 line from Aoki.

All teams try to maximize the values of their assets.

I doubt that Braun’s numbers would be affected greatly by switching OF corners.

I don’t know much about swing mechanics, but I’ve thought that Davis’s approach is somewhat interesting. He seems back-loaded and to be able to hold back his swing for breaking pitches, which is a useful quality in a power hitter. Pitch FX data is obviously volatile, but Davis generally killed off-speed stuff this year. That’s not something I would expect to see from a hitter with a bad swing.

In writing an article like this, I have to balance the needs of all readers. Some people really want to see every last detail, and others will stop reading if I provide more detail than I did. (Some probably tuned out despite my efforts to keep it simple). I will keep trying to find the perfect balance, but there is a practical limit to how much work can be shown, particularly if the formulas as applied are nested inside a spreadsheet anyway. The method is described in Derek Carty’s article cited above, and the data is drawn from Fangraphs, so it can be reproduced by anyone who wants to double-check or test alternative assumptions.

I used average major league player statistics, which is the default assumption for any player, and defensible to use for Davis and Gennett for the reasons I stated in the post above.

Gennett actually has had consistently high BABIPs through the minors. Hitters are generally believed to have an easier time sustaining higher BABIPs over time than pitchers are, particularly if they tend to make good contact.